Frame construction for a vehicle

ABSTRACT

A frame assembly is described including a tunnel, an engine cradle disposed forward of the tunnel and connected thereto, and a sub-frame disposed forward of the engine cradle and connected thereto. A forward support assembly extends upwardly from the subframe. An upper column extends upwardly from the engine cradle to connect with the forward support assembly. A rear brace assembly extends upwardly from the tunnel to connect with the forward support assembly and the upper column. In one embodiment, the frame assembly further includes an engine disposed in the engine cradle. An endless track is operatively connected to the engine and disposed beneath the tunnel for propulsion. A pair of skis is operatively connected to a steering device for steering. In another embodiment, the frame assembly further includes an engine disposed in the engine cradle. A rear wheel is operatively connected to the engine and disposed beneath the tunnel for propulsion, and two front wheels are operatively connected to a steering device for steering.

This application is a continuation application of U.S. application Ser.No. 09/877,212, filed on Jun. 11, 2001, which is incorporated herein byreference. Through 09/877,212, this application claims priority to U.S.application Ser. No. 60/237,384, filed Oct. 4, 2000, and is acontinuation-in-part of U.S. application Ser. No. 09/472,133, entitled“IMPROVED VEHICLE” filed on Dec. 23, 1999, now abandoned, the entirecontents of both applications are incorporated herein by reference.Through U.S. application Ser. No. 09/472,133, this application claimspriority to Canadian Patent Application No. 2,256,944, filed Dec. 23,1998, the entire contents of which are incorporated herein by reference.The present application also incorporates by reference U.S. applicationSer. No. 09/472,134, entitled “SNOWMOBILE,” filed Dec. 23, 1999, andU.S. patent application Ser. No. 60/230,432, entitled “A NOVELTHREE-WHEELED VEHICLE,” filed Sep. 6, 2000.

FIELD OF THE INVENTION

The present invention relates to the construction of vehicles such assnowmobiles, all terrain vehicles (“ATVs”), and other similar vehicles.More specifically, the present invention concerns the construction of aframe and related structural elements that enhance the ruggedness andability of such vehicles to operate across a wide variety of differentterrains and under a wide variety of conditions. In addition, thepresent invention concerns the design and construction of a frame forsnowmobiles, ATVs, and related vehicles that facilitate the constructionof such vehicles with an improved rider positioning.

DESCRIPTION OF RELATED ART AND GENERAL BACKGROUND

Snowmobiles, ATVs, and related vehicles (hereinafter, “recreationalvehicles,” although the appellation should not be construed to belimited only to the vehicles or type of vehicles described herein) oftenfunction under similar operating conditions. Despite this, snowmobiles,ATVs, and other recreational vehicles often do not share a common designapproach or a commonality of components. This is due, in large part, tothe different stresses and strains (mainly at the extremes) that thedifferent vehicles experience during routine operation.

Specifically, snowmobiles are designed with frame assemblies andsuspensions that easily absorb the shock of obstacles encountered ongroomed trails and in deep snow. They are also designed to handle theforces generated when the snowmobile is driven aggressively (e.g., underracing conditions). In addition, their frame assemblies are designed toprovide optimum steering and performance in snow, whether on groomedsnowmobile trails (packed snow) or in ungroomed, off-trail areas (powderor natural snow).

ATVs, on the other hand, are designed with suspensions and frameassemblies that are expected to absorb the type of momentarily intenseforces associated with more rugged terrain, specifically of the typeencountered in forests and woodland environments. In addition, an ATVframe is designed to withstand forces associated with significanttorsional stresses that are typical when an ATV straddles large objectsor when the wheels are disposed at different elevations because of theextreme terrain in which the ATV often operates.

It should be kept in mind that the design parameters of the frameassemblies for these two vehicles are also different. In a snowmobile,the frame at the rear of the vehicle is only about 15 inches wide. Thisis sufficient to cover the endless track that propels the vehicle and toprovide a seating area for the driver. The narrow width, however,imposes certain design restrictions on the vehicle. ATVs, on the otherhand, are designed with a significantly wider base, which is typically50 inches or more. This width also imposes certain design restrictionson the ATV.

Snowmobiles and ATVs are also designed with different centers ofgravity. In the typical snowmobile, the center of gravity is very low.This assists the snowmobile rider when he or she is on a slope or in aturn because the snowmobile will naturally resist the tendency to leanor tip. ATVs, on the other hand, like off-road trucks and the like, areexpected to traverse taller objects. Accordingly, their frames aredesigned so that the engine and seating area is further from the groundthan a snowmobile. Thus, ATVs have higher centers of gravity.

Naturally, since both vehicles are designed with off-road use in mind,there are similarities between the two. Both are provided with ruggedframes. Moreover, both are provided with strong suspensions. Despitethis, there have been few vehicles designed that capitalize on thesesimilarities.

Recognizing this basic similarity between the two vehicles, someafter-market designers have developed kits that permit snowmobiles to beconverted to ATVs and vice-versa. However, such kits are limited intheir effectiveness because the two vehicles are so completely differentfrom one another in their basic designs. The resulting, convertedvehicles suffer from drawbacks that are associated with the purpose forwhich the primary vehicle was designed. For example, a snowmobileconverted to an ATV is not expected to be able to traverse the same typeof terrain as a pure ATV. Similarly, an ATV that has been converted to asnowmobile is not expected to be able to traverse the same terrain thata pure snowmobile can.

Partly due to the consumer's use of snowmobiles in the winter and ATVsin the summer, the evolution of both snowmobiles and ATVs has convergedin recent years. Also, in recent years, designers have begun to applythe same basic design concepts to both vehicle types. What has resultedis a recognition that vehicles may be designed that incorporate many ofthe same structural elements and follow very similar design approaches.

The basis for the present invention stems from this basic recognition.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide a frameassembly with a tunnel, an engine cradle disposed forward of the tunneland connected thereto, and a sub-frame disposed forward of the enginecradle and connected thereto. The frame assembly further includes aforward support assembly extending upwardly from the subframe, an uppercolumn extending upwardly from the engine cradle to connect with theforward support assembly, and a rear brace assembly extending upwardlyfrom the tunnel to connect with the forward support assembly and theupper column.

It is another object of the present invention to provide a frameassembly wherein the forward support assembly, the upper column, and therear brace assembly connect at an apex above the upper column.

Another object of the present invention is to provide a frame assemblywhere the forward support assembly and the rear brace assembly form apyramidal construction.

A further object of the present invention is to provide a frame assemblyfurther including a steering bracket connected at the apex forsupporting a steering shaft at its upper end. In an alternateembodiment, the steering bracket may include a plurality of pairs ofholes for positioning of the steering shaft in a plurality of positions.

One other object of the present invention is to provide a frame assemblythat also includes an engine disposed in the engine cradle and anendless track operatively connected to the engine and disposed beneaththe tunnel for propulsion. In this embodiment, a pair of skis areoperatively connected to a steering device for steering.

Still another object of the present invention is to provide a frameassembly with an engine disposed in the engine cradle and a rear wheeloperatively connected to the engine and disposed beneath the tunnel forpropulsion. In this embodiment, two front wheels operatively connectedto a steering device for steering.

It is yet another object of the present invention to provide a frameassembly for a vehicle that includes a tunnel and an engine cradleadapted to receive an engine therein. A rear brace assembly is attachedto the tunnel at a point between its front and rear ends and extendsupwardly therefrom. A forward support assembly is attached to the rearbrace assembly and extends forwardly and downwardly therefrom. In afurther variation of this frame assembly, the rear brace assemblycomprises a left and a right leg and the forward support assemblycomprises a left and a right leg. The left and right legs of the rearbrace assembly and the forward support assembly connect to one anotherat an apex to form a pyramidal structure above the tunnel and enginecradle.

Still other objects of the present invention will be made apparent bythe discussion that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully described in conjunction with thefollowing drawings wherein:

FIG. 1 is a side-view schematic illustration of a prior art snowmobile,showing the prior art positioning of a rider thereon;

FIG. 2 is a side view illustration of the exterior of a snowmobileconstructed according to the teachings of the present invention, alsoshowing the positioning of a rider thereon;

FIG. 3 is an overlay comparison between the a prior art snowmobile (ofthe type depicted in FIG. 1) and a snowmobile constructed according tothe teachings of the present invention (as shown in FIG. 2),illustrating the difference in passenger positioning, among otherfeatures;

FIG. 4 is an exploded view of a frame assembly representative of thetype of construction typical of a snowmobile assembled according to theteachings of the prior art (specifically, the view illustrates thecomponents of a 2000 model year Ski-Doo® Mach™ Z made by Bombardier Inc.of Montréal, Québec, Canada);

FIG. 5 is a side view schematic illustration of the snowmobileillustrated in FIG. 2, with the fairings and external details removed toshow some of the internal components of the snowmobile and theirpositional relationship to one another;

FIG. 6 is a perspective illustration of a portion of the frame assemblyof the present invention, specifically the portion disposed toward therear of the vehicle;

FIG. 7 is a perspective illustration of a forward support frame, whichconnects with the portion of the frame assembly depicted in FIG. 6;

FIG. 8 is a front view illustration of an upper column of the frameassembly shown in FIG. 6;

FIG. 9 is a left side view illustration of the upper column depicted inFIG. 8;

FIG. 10 is a right side view illustration of the upper column shown inFIG. 8;

FIG. 11 is a perspective illustration, from the front left side, of atunnel portion of the frame assembly of the present invention;

FIG. 12 is another perspective illustration, from the rear left side, ofthe tunnel portion of the present invention shown in FIG. 11;

FIG. 13 is a perspective illustration, from the front left side, showingthe combination of the frame assembly depicted in FIG. 6 connected tothe tunnel portion depicted in FIGS. 11 and 12;

FIG. 14 is a perspective illustration, from the rear left side, showingthe combination of the frame assembly depicted in FIG. 6 connected tothe tunnel portion depicted in FIGS. 11 and 12 and also showing aportion of a front suspension assembly;

FIG. 15 is a perspective illustration, from the front left side, of someof the components that are part of the front suspension assemblydepicted in FIG. 14;

FIG. 16 is a perspective illustration, from the front left side, of aportion of a sub-frame that is part of the front suspension assemblyillustrated in FIG. 15;

FIG. 17 is another perspective illustration, from the front left side,of the front suspension assembly for a snowmobile, constructed accordingto the teachings of the present invention, showing the positionalrelationship between the parts illustrated in FIG. 15 and the sub-frameillustrated in FIG. 16;

FIG. 18 is a side view schematic of the frame assembly of the presentinvention showing the positional relationship between the frame assemblyand the engine, among other components;

FIG. 19 is a perspective illustration, from the left side, of the frameassembly according to the teachings of the present invention, alsoshowing the positional relationship between the frame assembly, theengine, and the front suspension;

FIG. 20 is another perspective illustration, from the front left side,of the combined frame assembly and tunnel portion constructed accordingto the teachings of the present invention, also showing the positionalrelationship between the frame assembly, the engine, and the frontsuspension;

FIG. 21 is a front perspective illustration of the embodiment depictedin FIG. 20;

FIG. 22 is a perspective illustration of a slightly different embodimentfrom the one depicted in FIG. 20;

FIG. 23 is a schematic side view illustration of the frame assembly ofthe present invention as embodied in a wheeled vehicle;

FIG. 24 is a schematic side view illustration of the frame assembly ofthe present invention as embodied in a slightly modified version of awheeled vehicle;

FIG. 25 is an enlarged side view illustration of the frame assembly ofthe present invention as embodied in the wheeled vehicle shown in FIG.24;

FIG. 26 is a perspective illustration, from the left rear, of the frameassembly of the present invention, showing some of the detail of thefront suspension incorporated into the wheeled vehicle shown in FIGS. 23and 24;

FIG. 27 is a perspective illustration, from the front left, showing theframe assembly of the present invention as depicted in FIG. 26;

FIG. 28 is a perspective illustration, from the rear left side of analternate embodiment of the frame assembly of the present invention;

FIG. 29 is a side view illustration of the frame assembly shown in FIG.28;

FIG. 30 is a top view of the frame assembly depicted in FIG. 28;

FIG. 31 is a side view illustration of the frame assembly shown in FIG.29, illustrating the variable positioning of the handlebars that ispossible with this embodiment of the present invention;

FIG. 32 is a perspective illustration of the embodiment shown in FIG.31, showing in greater detail the variations in positioning of thehandlebars that is made possible by the construction of the presentinvention;

FIG. 33 is a close-up side-view detail of the connection point betweenthe handlebars and the frame assembly of the present invention,illustrating the variable positioning of the handlebars;

FIG. 34 is a further illustration of the variable positioning feature ofthe present invention; and

FIG. 35 is a graph showing the vertical displacement rate of the frameof the present invention in comparison with a prior art Bombardiersnowmobile (the ZX™ series) and a prior art snowmobile made by ArcticCat.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before delving into the specific details of the present invention, itshould be noted that the conventions “left,” “right,” “front,” and“rear” are defined according to the normal, forward travel direction ofthe vehicle being discussed. As a result, the “left” side of asnowmobile is the same as the left side of the rider seated in aforward-facing position on the vehicle (or travelling in a forwarddirection on the vehicle).

FIG. 1 illustrates a rider operator 10 sitting on a prior art snowmobile12. Rider 10 is positioned on seat 14, with his weight distributed overendless track 16. Motor 18 (shown in general detail) is located overskis 20. As with any snowmobile, endless track 16 is operativelyconnected to motor (or engine) 18 to propel snowmobile 12 over the snow.Motor or engine 18 typically is a two-stroke internal combustion engine.Alternatively, a 4-stroke internal combustion engine may be substitutedtherefor. In addition, any suitable engine may be substituted therefor.

FIG. 2 provides a side view of a snowmobile 22 constructed according tothe teachings of the present invention. Here, rider/operator 24 is shownin a more forward, motor cross racing-like position, which is one of theaspects of the present invention. In this position, the weight ofoperator 24 is forward of the position of rider 10 in the prior artexample.

The positioning of rider 24 closer to motor 36 offers several advantagesthat are not achieved by the prior art. For example, since rider 24 ispositioned closer to the engine 36, the center of gravity of rider 24 iscloser to the center of gravity of the vehicle, which is often at thedrive axle of the vehicle or near thereto. In other words, rider 24 hashis weight distributed more evenly over the center of gravity of thevehicle. As a result, when the vehicle traverses rough terrain, rider 24is better positioned so that he does not experience the same impact froman obstacle as rider 10 on snowmobile 12. The improved rider positioningillustrated in FIG. 2 also improves the rider's ability to handle thevehicle.

FIG. 2 illustrates the basic elements of snowmobile 22. Snowmobile 22includes an endless track 26 at its rear for propulsion. A rearsuspension 28 connects endless track 26 to the vehicle frame. Snowmobile22 also includes a front suspension 30. Skis 32, which are operativelyconnected to handlebars 34, are suspended from the front suspension 30for steering the vehicle. A motor or engine (preferably, an internalcombustion engine) 36 is located at the front of snowmobile 22, aboveskis 32. Operator 24 is seated on a seat 38, which is positioned abovethe endless track 26.

Three positional points of particular relevance to the present inventionare also shown in FIG. 2. Specifically, seat position 40, foot position42, and hand position 44 of operator 24 are shown. In the modifiedseating position of operator 24, which is made possible by the teachingsof the present invention, hand position 44 is forward of foot position42, which is forward of seat position 40. The three positions definethree angles, a, b, and c between them that help to define the seatingposition of operator 24, which permits rider 24 to be closer to centerof gravity 45 of the vehicle. Moreover, hand position 44 is forward ofcenter of gravity 45 of snowmobile 22.

FIG. 3 provides an overlay between prior art snowmobile 12 andsnowmobile 22 constructed according to the teachings of the presentinvention. Rider 10 (of prior art snowmobile 12) is shown in solid lineswhile operator 24 (of snowmobile 22) is shown in dotted lines forcomparison. The comparative body positions of rider 10 and operator 24are shown. As is apparent, the present invention permits theconstruction of a snowmobile 22 where the rider 24 is in a more forwardposition. Moreover seat position 40, foot position 42, and hand position44 differ considerably from seat position 46, foot position 48, and handposition 50 in the prior art snowmobile 12. In this position, the centerof gravity of operator 24 is closer to center of gravity 45 ofsnowmobile 22 than in the prior art example.

As a basis for comparison with the figures that provide the details ofthe present invention, FIG. 4 provides an exploded view of a frameassembly 52 for a snowmobile constructed according to the teachings ofthe prior art. Frame assembly 52 includes, as its major components, atunnel 54 and an engine cradle 56. As illustrated, engine cradle 56 ispositioned in front of tunnel 54. Engine cradle 56 receives motor 18.

As shown in FIG. 4, tunnel 54 is basically an inverted U-shapedstructure with a top plate 58 integrally formed with left and right sideplates 60, 62, respectively. Top plate 58 provides the surface onto withseat 14 is mounted, as would be known to those skilled in the art. Footboards 64 (of Which only the left foot board is visible in FIG. 4) areintegrally formed with the side plates 60, 62 and extend outwardly,perpendicular to the plane of side plates 60, 62. Foot boards 64 providea location on which rider 10 may place his feet during operation ofsnowmobile 12. While top plate 58, side plates 60, 62, and foot boards64 are preferably formed from aluminum, any suitable alternativematerial may be used, as would be recognized by those skilled in theart. Moreover, while top plate 58, side plates 60, 62 and footboards 64are shown as an integral structure, an integral construction is notrequired. Instead, top plate 58, side plates 60, 62, and foot boards 64may be separately manufactured and connected to one another by anysuitable means known in the art.

FIG. 4 also shows that engine cradle 56 is connected to tunnel 54 by anysuitable means known to those skilled in the art. For example, enginecradle 56 may be welded or bolted to tunnel 54. Engine cradle includes abottom plate 66 and left and right side walls 68, 70, which are providedwith left and right openings 72, 74, respectively. Left opening 72 isprovided so that the shafts for the transmission (typically acontinuously variable transmission or CVT) may extend outwardly fromleft wall 68. The shafts that connect the engine 18 to the transmissionpass through left opening 72. A gearbox (not shown) typically isprovided on the right side of snowmobile 10. The shafts that connectengine 18 to the gearbox pass through right opening 74. Left and rightopenings 72, 74 also allow heat from engine 18 to be radiated fromengine cradle 56, which assists in cooling engine 18.

As FIG. 4 illustrates, left side wall 68 is provided with a beam 76 thatis removably connected thereto. Beam 76 may be removed during servicing,for example, to facilitate access to the engine components andperipheral elements disposed within left opening 72.

FIG. 4 also illustrates the placement of a handlebar support element 78,which connects to the rear of engine cradle 56. Handlebar supportelement 78 is generally an inverted U-shaped structure that extendsupwardly from the combined engine cradle 56 and tunnel 54. A bracket 80is positioned at the midpoint of handlebar support element 78 andprovides structural support for handlebars 82, which is used to steersnowmobile 12.

To provide an improved driver positioning, as described above, theinventors of the present invention appreciated the advantages of movinghandlebars 82 forward of the position shown in FIG. 1. To do this,however, required a novel approach to the construction of frame assembly52 of snowmobile 12. The redesign resulted in the present invention,which is described in detail below.

As illustrated in FIG. 5, snowmobile 22 incorporates a completelyredesigned frame assembly 84. Frame assembly 84 includes, among otherelements, tunnel 86, engine cradle 88, and over-arching frame elements90. As with snowmobile 12, snowmobile 22 includes a seat 94 on whichrider 24 sits while operating snowmobile 22. Tunnel 86 is connected to arear suspension 96 that contains a number of wheels 98 disposed on aslide frame 100 around which an endless track 102 rotates to propelsnowmobile 22 across the snow.

Endless track 102 is connected to engine 104 (preferably a two or fourstroke internal combustion engine) positioned within engine cradle 88.Endless track 102 is connected to engine 104 through a transmission 106,which is preferably a continuously variable transmission (or “CVT”), asis known in the art.

Two skis 108 are provided at the front of snowmobile 22 for steering.Skis 108 are connected to engine cradle 88 through a front suspension110. Front suspension 110 connects to skis 108 through a pivot joint 112on the top of skis 108. Skis 108 are operatively connected to a steeringshaft 114 that extends over engine 104. Steering shaft 114 is connected,in turn, to handlebars 116, which are used by operator 24 to steersnowmobile 22.

FIG. 6 illustrates the individual elements of rear frame assembly 84 ingreater detail. Rear frame assembly 84 includes an upper column 118,which is an inverted U-shaped structural element. If necessary, uppercolumn 118 may be reinforced with a cross-member 120, but this is notneeded to practice the present invention. A left brace 122 and a rightbrace 124 are connected to a bracket 126 above upper column 118. Abushing or bearing (or other similar element) 128 is attached to bracket126 and accepts steering shaft 114 therethrough. It also securessteering shaft 114 to rear frame assembly 84. Left and right braces 122,124 include left and right brackets 130, 132 at their lower portions.Left and right brackets 130, 132 secure left and right braces 122, 124to tunnel 86 of snowmobile 22.

It should be noted that, while the construction of frame assembly 84 isillustrated involves the use of tubular members, frame assembly 84 mayalso be constructed according to a monocoque or pseudo-monocoquetechnique. A monocoque construction is one where a single sheet ofmaterial is attached to an underlying frame (such as with theconstruction of an aircraft). The skin applied to the frame addsrigidity to the underlying frame structure. In a similar manner, apseudo-monocoque technique provides a rigid structure by providing aframe constructed from a single sheet of material.

Instead of constructing frame assembly 84 from a number of tubularmembers, frame assembly 84 may be constructed from a single sheet ofmaterial (such as aluminum) that has been pressed or molded into theappropriate shape using a pseudo-monocoque manufacturing technique. Aswould be understood by those skilled in the art, this would result in aconstruction that has a high strength with a low weight.

FIG. 7 illustrates a forward support assembly 134 (also called fronttriangle 134), which connects to bracket 126 and extends forwardly ofbracket 126. Forward support assembly 134 includes a bracket 136 at itsrear end that connects to bracket 126 of frame assembly 84 (preferablybolted). Forward support assembly 134 also has left and right braces138, 140 that extend forwardly and downwardly from bracket 136 and areconnected thereto preferably by welding. Left and right braces 138, 140are connected at their forward ends by a cross-member 142, whichincludes a plurality of holes 144 therein to lighten the weight thereof.Left and right connecting brackets 145, 146 are connected tocross-member 142. The left and right connecting brackets 145, 146connect, in turn, to front suspension 110.

FIGS. 8, 9, and 10 illustrate upper column 118 in greater detail. Asdescribed above, upper column 118 is essentially an inverted U-shapedmember that is preferably tubular in shape to facilitate itsconstruction. Upper column 118 preferably is bent into the appropriateshape from a straight tube with the dimensions shown. As would beunderstood by those skilled in the art, however, upper column 118 neednot be made as a tubular member.

Upper column 118 has left and right legs 148, 150 that extend downwardlyfrom an apex 152. A bracket 154 is disposed at apex 152 for connectionto bracket 126 of frame assembly 84. Preferably, bracket 154 is weldedat the apex of upper column 118 (however any other suitable attachmentmeans is possible). Left leg 148 includes a bracket 156 at itslower-most portion that connects left leg 148 to engine cradle 88.Similarly, right leg 150 includes a bracket 158 at its lower-mostportion to connect right leg 150 to engine cradle 88. Preferably,brackets 156, 158 are welded to upper column 118. Left and right legs148, 150 preferably attach to engine cradle 88 via bolts or othersuitable fasteners.

FIGS. 11 and 12 illustrate tunnel 86 in greater detail. Tunnel 86includes a top plate 160 with left and right downwardly extending sideplates 162, 164. A left foot rest 166 extends outwardly from the bottomof left side plate 162. Similarly, a right foot rest 168 extendsoutwardly from the bottom portion of right side plate 164. Left andright foot rests 166, 168 provide a location along tunnel 86 onto whichrider 24 may place his or her feet while operating snowmobile 22.

Left side plate 162 extends forwardly beyond the front portion 170 oftunnel 86 to form a left engine cradle wall 172. Similarly, right sideplate 164 extends forwardly of front end 170 of tunnel 86 to form rightengine cradle wall 174. At the lower edge of left and right enginecradle walls 172, 174, there are laterally extending portions 176, 178,which serve to strengthen left and right engine cradle walls 172, 174.Removable elements 180 extend between left foot rest 166 and leftlaterally extending portion 176. Removable portions 180 may or may notbe removed between left foot rest 166 and left laterally extendingportion 176. FIG. 11 shows removable portions 180 removed, while FIG. 12shows removable portions 180 not removed. It should be noted that thesame removable portions 180 may or may not extend between right footrest 168 and right laterally extending portion 178.

Left engine cradle wall 172 preferably includes an opening 182therethrough. Opening 182 permits the shafts from transmission 106 topass therethrough. Unlike left engine cradle wall 172, right enginecradle wall 174 does not include such an opening. Instead, right enginecradle wall 174 is essentially solid. Due to its construction, rightengine cradle wall 174 reflects radiant heat from engine 104 back toengine 104 to assist in minimizing heat dissipation from engine 104.Left and right openings 184, 186 are provided through left and rightengine cradle walls 172, 174 so that a drive shaft 188 may passtherethrough. Drive shaft 186 connects to endless track 102 forpropulsion of snowmobile 22. Opening 182 may include a member 189 aboutits periphery, also as illustrated in FIGS. 11 and 12, that providesclearance for the engine. Left engine cradle wall 172 also includes anopening 192 above opening 184 through which a shaft passes for part oftransmission 106.

FIGS. 13 and 14 illustrate a combination of a variation of frameassembly 190 connected to tunnel 86. Frame assembly 190 includes uppercolumn 118 as illustrated in FIGS. 8-10. However, frame assembly 190differs somewhat from frame assembly 84. For example, left and rightbraces 194, 196 are shaped so that they extend outwardly from thepositions defined by left and right braces 122, 124. As illustrated,left and right braces 194, 196 include elbows 198, 200. A cross-brace202 optionally may be placed between left and right braces 194, 196 toadd structural rigidity to frame assembly 190. As with frame assembly84, a bracket 126 is provided at apex 204 where left and right braces194, 196 meet one another. Forward support assembly 134 is the same asdepicted in FIG. 7. A front engine cradle wall 206 is also shown in FIG.13.

FIGS. 15-17 illustrate various aspects of front suspension 110 andassociated structures. While the figures illustrate the embodimentpreferably used in combination with snowmobile 22, it should berecognized that front suspension 110 may also be used in combinationwith a wheeled vehicle, as will be discussed in connection with FIGS.23-27.

Front suspension 110 includes left and right ski legs 208, 210. Left andright ski legs 208, 210 are preferably made from aluminum and arepreferably formed as extrusions. While an aluminum extrusion ispreferred for left and right ski legs 208, 210, those skilled in the artwould appreciate that ski legs could be made from any suitable materialand in any acceptable manner that would provide similar strength and lowweight characteristics. Left and right ski legs 208, 210 include holes212, 214 through which a fastener (not shown) is disposed to pivotallyconnect skis 32 to snowmobile 22, as shown in FIG. 2.

Left and right ski legs 208, 210 are movably connected to left and rightsupport arms 216, 218. Left and right suspension arms 216, 218 includelower left and right suspension support arms 220, 222 and upper left andright suspension support arms 224, 226.

As shown in FIGS. 15 and 17, lower left suspension support arm 220connects to left ski leg at lower left attachment point 228 preferablythrough a ball joint (not shown) so that left ski leg 208 may pivot androtate with respect to lower left suspension support arm 220. Similarly,lower right suspension support arm 222 connects to right ski leg 210 atlower right attachment point 230, preferably through a ball joint. Upperleft suspension support arm 224 preferably attaches to left ski leg 208at upper left attachment point 232, preferably through a ball joint orother suitable means. In addition, upper right suspension support arm226 connects to right ski leg 210 at upper right attachment point 234through a ball joint or other suitable means.

Lower left suspension support arm 220 includes front and rear members236, 238, which meet at apex 240 where they connect with left lowereyelet 242. Front member 236 includes a joint 244 at an inner end, andrear member 238 includes a joint 246 also at an inner end. Similarly,lower right suspension support arm 222 includes front and rear members248, 250, which meet at apex 252 where they connect with right lowereyelet 254. Front member 248 includes a joint 256 at an inner end andrear member 250 includes a joint 258 also at an inner end.

Upper left suspension support arm 224 includes front and rear members260, 262, which meet at apex 264 where they connect with upper lefteyelet 266. Front member 260 includes a joint 268 at an inner end, andrear member 262 includes a joint 270 also at an inner end. Similarly,upper right suspension support arm 226 includes front and rear members272, 274, which meet at apex 276 where they connect with upper righteyelet 278. Front member 272 includes a joint 280 at an inner end andrear member 274 includes a joint 282 also at an inner end.

At a point inward from apex 240, lower left suspension support arm 220includes a left bracket 284 that is connected to and extends partiallyalong front and rear members 236, 238. Similarly, lower right suspensionsupport arm 222 includes a right bracket 286 that is connected to andextends partially along front and rear members 248, 250. Slidablyattached to rear member 238 of lower left suspension arm 220 is a leftpivot block 288. A right pivot block 290 is slidably attached to rearmember 250 of lower right suspension support arm 222. A stabilizer bar292 is connected between left and right pivot blocks 288, 290.Stabilizer bar 292 is adapted to slide and pivot by way of left andright pivot blocks 288, 290. These blocks 288, 290 slide relative toleft and right lower suspension support arms 220, 222. Left and rightbushings 296, 298 are provided to allow some rotation of the componentsof front suspension 110. Left and right ski legs 208, 210 rotatablyconnect to front suspension 110 for facilitating movement of skis 32.

FIG. 16 illustrates sub-frame 294, which is essentially a unitary,V-shaped structure. Sub-frame 294, which forms a part of frontsuspension 110, includes a central channel 300 flanked on either side byleft and right upwardly extending panels 302, 304. Left upwardlyextending panel 302 includes a left lower panel 306 connected to lefttransition structure 308 and left triangular panel 310. Similarly, rightupwardly extending panel 304 includes a right lower panel 312 connectedto right transition structure 314 and right triangular panel 316. Whilesub-frame 294 preferably is a unitary structure (an integrally-formedstructure), sub-frame 294 need not be constructed in this manner. Aswould be understood by those skilled in the art, sub-frame 294 may beassembled from a number of separate elements that are connected togetherby any suitable means such as by welding or by fasteners.

As illustrated in FIG. 17, sub-frame 294 is an integral part of frontsuspension 110 and connects to left support arm 216 and right supportarm 218 through a number of brackets 318 connected at various locationson sub-frame 294.

FIG. 18 is a side view of one embodiment of the completed frame assembly84 of the present invention. As shown, over-arching frame elements 90are connected between tunnel 86 and sub-frame 294 to establish an apex320 to which steering shaft 114 is connected.

FIG. 19 is a perspective illustration of the embodiment of the presentinvention shown in FIGS. 13 and 14 to assist in understanding the scopeand content of the present invention. As illustrated, drive shaft 322extends through left opening 182 in left engine cradle wall 172. Aportion of gearbox 324 is also visible. In addition, left shock absorber326, which is connected between cross-member 142 and left support arm216, is illustrated. Right shock absorber, which extends betweencross-member 142 and right support arm 218 is visible in FIG. 20.Furthermore, left forward foot wall 330 is shown at the forward end ofleft foot rest 166. A similar forward foot wall may be provided on theright side of snowmobile 22 (but is not illustrated herein).

FIGS. 20 and 21 illustrate further details of the present invention byshowing the various elements from slightly different perspective views.FIG. 22 illustrates the modified version of the elements of the presentinvention shown in FIGS. 6 and 7. Here, left and right braces 122, 124are illustrated instead of left and right braces 194, 196. As discussedpreviously, left and right braces 122, 124 differ from left and rightbraces 194, 196 in that they are not bent but, instead, are straightelements of overarching frame 90. The same left and right braces 122,124 are shown in FIG. 18. As would be understood by those skilled in theart, the two different embodiments of these braces are interchangeable.In addition, their shape may be altered depending on the requirements ofthe particular vehicle design, as would be understood by those skilledin the art.

Left and right braces 194, 196 are bent to accommodate an airbox (notshown) between them. Left and right braces 122, 124 are not bent becausethey do not need to accommodate an airbox.

FIG. 20 also illustrates steering gear box 115 at the bottom end ofsteering shaft 114 that translates the movement of handlebars 116 into asteering motion of skis 32.

FIGS. 23-27 illustrate alternate embodiments of the present inventionthat are designed for a wheeled vehicle 332, rather than a snowmobile22. For the most part, the elements designed for wheeled vehicle 332 arethe same as those for snowmobile 22, except for those elements requiredto attach wheels 334 to wheeled vehicle 332.

In the preferred embodiment of wheeled vehicle 332, the vehicle includestwo front wheels 334 and a single rear wheel 336. As would be understoodby those skilled in the art, however, wheeled vehicle 332 may beconstructed with two rear wheels rather than one. If so, wheeled vehicle332 would be a four-wheeled vehicle rather than the three-wheeledvehicle shown.

Wheeled vehicle 332 includes a seat 338 disposed over tunnel 86 in thesame manner as snowmobile 22. The vehicle includes engine 104 at itsforward end, encased by fairings 340. Fairings 340 protect engine 104and provide wheeled vehicle 332 with an aesthetically pleasingappearance. Engine 104 is connected to CVT 106, which translates thepower from engine 104 into motive power for wheeled vehicle 332.

As shown in FIG. 23, CVT 106 is connected by suitable means to driveshaft 342, which is connected to rear wheel 336 by a drive chain 344. Asprocket 346 is connected to drive shaft 342. A similar sprocket 348 isprovided on the shaft connected to rear wheel 336. Drive chain 344 is anendless chain that connects sprockets 346, 348 to one another. To stopwheeled vehicle 332 during operation, disc brakes 350 are connected tofront wheels 334. Disc brakes 350 clamp onto discs 352 to slow or stopwheeled vehicle 332 in a manner known to those skilled in the art.

A rear suspension 354 is provided under tunnel 86. Rear suspension 354absorbs shocks associated with the terrain over which wheeled vehicle332 travels. Rear suspension 354 replaces rear suspension 28 onsnowmobile 22.

FIG. 24 illustrates an alternate embodiment of wheeled vehicle 356.Wheeled vehicle 356 differs in its construction at the rear.Specifically, rear end 358 is shorter than that shown for wheeledvehicle 332. In addition, wheeled vehicle 356 includes a four strokeengine, rather than the two stroke engine 104 illustrated for wheeledvehicle 332. Also, wheeled vehicle 356 includes a manual speedtransmission 360 (with a clutch) rather than continuously variabletransmission 106, as illustrated with other embodiments of the presentinvention. Both constructions of the wheeled vehicle, as well as manyother variations, are contemplated within the scope of the presentinvention. In addition, as discussed above, the present invention may beused with a two or four stroke engine (or any other type of engine thatprovides the motive power for the vehicle).

FIG. 25 illustrates in greater detail the embodiment of the presentinvention shown in FIG. 24.

FIGS. 26-27 illustrate the basic frame assembly contemplated for wheeledvehicles 332, 356. For either vehicle, the construction of frameassembly 191 is similar to that previously described. This embodimentdiffers in that left and right wheel knuckles 366, 368 are provided sothat wheels 334 may be attached thereto. In most other respects, theconstruction of frame assembly 191 is the same as that previouslydescribed.

The variable geometry of steering shaft 364 will now be described inconnection with FIGS. 28-34.

As illustrated in FIG. 28, left brace 122 and right brace 124 extendupwardly from tunnel 370 to apex 372 where they connect to variablegeometry steering bracket 374. Upper column 118 extends from left enginecradle wall 376 and right engine cradle wall 174 and also connects tovariable geometry steering bracket 374. Forward support assembly 134extends from sub-frame 294 to variable geometry steering bracket 374.

Variable geometry steering bracket 374 is essentially a U-shaped elementwith a rear end 376 and a forward end 378. At rear end 376, a firstcross-member 380 extends between left and right legs 382, 384 ofvariable geometry steering bracket 374 to define a closed structure. Asecond cross member 386 extends between left and right legs 382, 384forward of first cross member 380 and defines a U-shaped opening 387toward forward end 378 of variable geometry steering bracket 374. Afirst pair of holes 388 and a second pair of holes 390 are disposedthrough left and right legs 382, 382 of variable geometry steeringbracket 374 and provide separate attachment points for steering shaft364. FIG. 29 illustrates the same structures in side view and FIG. 30illustrates the same structures in top view.

This embodiment of the frame assembly of the present invention differsfrom the previous embodiments in a few respects. First, left enginecradle wall 393 includes a C-shaped opening 392 instead of opening 182.C-shaped opening 392 facilitates maintenance of an engine (not shown) inengine cradle 394. Second, an elongated radiator 396 is integrated intotunnel 370. Radiator 396 includes an inlet 398 and an outlet 400 thatare connected to the cooling system of the engine to assist in reducingthe temperature of the coolant therein. To facilitate dissipation ofheat, radiator 396 includes fins 402 on its underside.

FIG. 31 provides another side view of the frame assembly of the presentinvention and illustrates the two positions of steering shaft 364 madepossible by the construction of variable geometry steering bracket 374.To accommodate the variable geometry of steering shaft 362 andhandlebars 116, steering shaft 364 includes a bend 402 at its lower end.Steering shaft 364 passes through a bearing or bushing (not shown) atits upper end that is connected to variable geometry steering bracket374 at either of first or second pairs of holes 388, 390. By selectingeither first or second pairs of holes 388, 390, first and secondhandlebar positions 404, 406 are selectable. As would be recognized bythose skilled in the art, however, variable geometry steering bracket374 may be provided with greater that two pairs of holes 388, 390 tofurther increase the variability handlebars 116. Also, variable geometrysteering bracket 374 may be provided with a construction that permitsinfinite variation of the position of handlebars, as would be understoodby those skilled in the art, should such a construction be desired.

FIGS. 32-34 provide additional views of the variable positioning of thehandlebars 116 to facilitate an understanding of the scope of thepresent invention.

Frame assembly 84, 190, 191 of the present invention uniquelydistributes the weight loaded onto the vehicle, whether it is snowmobile22 or one of wheeled vehicles 332, 356. Each of the main components ofthe frame assembly 84, 190, 191 forms a triangular or pyramidalconfiguration. All of the bars of the frame assembly 84, 190, 191 workonly in tension and compression, without bending. Therefore, each bar offrame assembly 84, 190, 191 intersects at a common point, the bracket126 (in the non-variable steering geometry) or variable geometrysteering bracket 374. With this pyramidal shape, the present inventioncreates a very stable geometry.

Specifically, the structure of frame assembly 84, 190, 191 enhances thetorsional and structural rigidity of the frame of the vehicle. Thisimproves handling. Usually, with a snowmobile, there is only a smalltorsional moment because the width of the snowmobile is only about 15inches. An ATV, on the other hand, has a width of about 50 inches and,as a result, experiences a significant torsional moment. Therefore, toconstruct a frame assembly that is useable in either a snowmobile or anATV, the frame must be able to withstand the torsional forces associatedwith an ATV.

Not only does frame assembly 84, 190, 191 reduce torsional bending, italso reduces the bending moment from front to rear. The increasedrigidity in both directions further improves handling.

In addition, the creation of frame assembly 84, 190, 191 has at leastone further advantage in that the frame can be made lighter and strongerthan prior art frame assemblies (such as frame assembly 52, which isillustrated in FIG. 4). In the conventional snowmobile, frame assembly52 included a tunnel 54 and an engine cradle 56 that were rivetedtogether. Because frame assembly 84, 190, 191 adds strength and rigidityto the overall construction and absorbs and redistributes many of theforces encountered by the frame of the vehicle, the panels that make upthe tunnel 86 and the engine cradle 88 need not be as strong or as thickas was required for the construction of frame assembly 52.

In the front of the vehicle, left and right shock absorbers 326, 328 areconnected to forward support assembly 134 so that the forces experiencedby left and right shock absorbers 326, 328 are transmitted to frameassembly 84, 190, 191. In the rear of the vehicle, the left and rightbraces 122, 124 are orientated with respect to the rear suspension.Upper column 118 is positioned close to the center of gravity of thevehicle's sprung weight. The sprung weight equals all of the weightloaded onto the vehicle's entire suspension. The positioning of theseelements such that they transmit forces encountered at the front, middleand rear of the vehicle to an apex creates a very stable vehicle that iscapable of withstanding virtually any forces that the vehicle mayencounter during operation without sacrificing vehicle performance.

FIG. 35 illustrates the degree to which the rigidity of a frameconstructed according to the teachings of the present invention isimproved. The highest line on the graph shows that for a 100 kg load,the vertical displacement of the frame of the present invention is only−2 mm. However, in the prior art Bombardier ZX™ model snowmobile, a loadof only 50 kg produced a vertical displacement of −6 mm. In addition, aload of about 30 kg on the frame for the prior art Arctic Cat®snowmobile produced a vertical displacement of −6 mm. In other words,the structural rigidity of the frame assembly of the present inventionis greatly improved.

While the invention has been described by way of example embodiments, itis understood that the words which have been used herein are words ofdescription, rather than words of limitation. Changes may be made,within the purview of the appended claims without departing from thescope and the spirit of the invention in its broader aspects. Althoughthe invention has been described herein with reference to particularstructures, materials, and embodiments, it is understood that theinvention is not limited to the particulars disclosed.

1. A snowmobile, comprising: a frame including a tunnel and an enginecradle forward of the tunnel; an engine mounted in the engine cradle; adrive track disposed below and supported by the tunnel and connectedoperatively to the engine for propulsion of the snowmobile; left andright skis disposed on the frame; a straddle seat disposed on the tunnelabove the drive track and rearward of the engine; a pair of footrestssupported by the frame; a steering column headpipelessly movablyconnected to the frame and operatively connected to the two skis; ahandlebar connected to the steering column; a pyramidal brace assemblyconnected to the frame, the assembly including: left and right rear legsextending forwardly and upwardly from the tunnel, each of the left andright rear legs having a front end and a rear end, the rear ends of therear legs being spaced further from each other than the front ends ofthe rear legs, and left and right front legs extending rearwardly andupwardly from the frame forward of the tunnel, each of the left andright front legs having a front end and rear end, the front ends of thefront legs being spaced further from each other than the rear ends ofthe front legs.
 2. The snowmobile of claim 1, wherein the pyramidalbrace assembly further includes a cross-member interconnecting the frontlegs.
 3. The snowmobile of claim 1, wherein the legs of the pyramidalbrace assembly form an apex not forward of the engine.
 4. The snowmobileof claim 1, wherein the front legs of the pyramidal brace assembly areforward of and above the steering column.
 5. The snowmobile of claim 1,wherein the rear ends of the front legs of the pyramidal brace assemblyand the front ends of the rear legs of the pyramidal brace assembly areinterconnected.
 6. The snowmobile of claim 1, wherein the rear ends ofthe front legs of the pyramidal brace assembly and the front ends of therear legs of the pyramidal brace assembly are interconnected and form anapex not forward of the engine.
 7. The snowmobile of claim 6, furthercomprising an upper column extending upwardly from the frame.
 8. Thesnowmobile of claim 7, wherein the upper column forms the apex with thefront ends of the rear legs of the pyramidal brace assembly and the rearends of the front legs of the pyramidal brace assembly.
 9. Thesnowmobile of claim 2, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.
 10. Thesnowmobile of claim 3, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.
 11. Thesnowmobile of claim 4, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.
 12. Thesnowmobile of claim 5, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.
 13. Thesnowmobile of claim 6, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.
 14. Thesnowmobile of claim 7, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.
 15. Thesnowmobile of claim 8, wherein: the frame further includes a sub-frameforward of the engine cradle, the snowmobile further comprises left andright suspension arms pivotally connected to the sub-frame on respectivesides of the sub-frame, and the left and right skis are disposed on theframe via a connection to the respective suspension arm.